Vibrating roller earth compactor

ABSTRACT

An earth compactor of the roller type having first and second rollers one behind the other in the direction of travel of the compactor, a vibrator for vibrating the first roller at a first frequency, and a vibrator for vibrating the second roller at a second frequency. The vibrators take the form of eccentrically mounted weights on shafts rotatable at different speeds along the axes of the respective rollers. In one embodiment the eccentric weights and the rollers each have the same size and mass. In another embodiment the slower rotating eccentric weights have a greater mass than the more rapidly rotating weights. In an additional embodiment, the slower rotating heavier weights vibrate a roller of greater mass than the roller vibrated by the smaller mass faster rotating weight. The rollers are mounted on a rigid frame for rotation and the effect of vibrating the rollers with vibrators operating at different constant frequencies is to vibrationally impact the rollers against the ground in a band of frequencies to insure uniform compaction of the ground regardless of variations in consistency of the earth to be compacted.

United States Patent 1 1 3,722,380 Kaltenegger 11 Mar. 27, 1973 [541 VIBRATING ROLLER EARTH COMPACTOR [57] ABSTRACT [76] Inventor: Benno Kaltenegger, Kurhausstr. 77- An earth compactor of the roller type having first and 79, I-Iennef, Germany [22] Filed: Dec. 15, 1970 [21] Appl. No.: 98,329

[30] Foreign Application Priority Data Jan. 17, 1970 Germany ..P 20 01 988.9

[52] US. Cl ..404/117 [51] Int. Cl ..E0lc 19/28 [58] Field of Search .,...94/50 V; 74/61, 87

[56] 1 "References Cited UNITED STATES PATENTS 3,595,145 7/1971 Mozdzanowski ..94/5O V 3,383,992 5/1968 Kaltenegger... ..94/50 V 3,435,741 4/1969 Mozdz anowski .94/50 V 3,580,147 5/1971 Kaltcngegger ..94/5O V Primary Examiner-Nile C. Byers, Jr.

second rollers one behind the other in the direction of travel of the compactor, a vibrator for vibrating the first roller at a first frequency, and a vibrator for vibrating the second roller at a second frequency. The vibrators take the form of eccentrically mounted weights on shafts rotatable at different speeds along the axes of the respective rollers. In one embodiment the eccentric weights and the rollers each have the same size and mass. In another embodiment the slowerrotating eccentric weights have a greater mass than the more rapidly rotating weights. In an additional embodiment, the slower rotating heavier weights vibrate a roller of greater mass than the roller vibrated by the smaller mass faster rotating weight. The rollers are mounted on a rigid frame for rotation and the effect of vibrating the rollers with vibrators operating at different constant frequencies is to vibrationally impact the rollers against the ground in a band of frequencies to insure uniform compaction of the ground regardless of variations in consistency of the earth to be compacted.

Att0rneyMarkva, Smith & Kruger 25 Claims, 8 Drawing Figures 5 8 7 8\ 'I V 1 i/ l PATENTEUmnzmrs 3. 722.380

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SHEET 3 [1F 3 IN VEN TOR 5W KW VIBRATING ROLLER EARTH COMPACTOR This invention relates generally to a roller type vibrating earth compactor and particularly to a road roller type compactor having at least two rolls which are disposed one behind the other in the direction of travel of the roller, are mounted on a rigid frame, and which are each vibrated by vibrating assemblies associated with the respective rollers.

It is known in the art to provide a vibrating road rolling machine with a device for imparting vibration to the rolls of the roller. Customary means for vibrating the rollers take the form of a shaft with eccentrically mounted weights for each roller. In the known prior constructions, the eccentrically mounted or unbalanced weights are normally mounted on shafts which are driven at the same speed so the frequency of the vibration transmitted to each roller is the same. Hence, in the known road rollers, both rollers'are vibrated at the same frequency, and in the case of soils or earths of varying consistencies the same degree of compaction is not obtained.

It is therefore an object of this invention to provide a roller type earth compacting machine or road roller including vibrating means which assure that the same degree of compaction is obtained in soils and earths of different consistencies. Accordingly, the present invention relates to a roller type compacting machine having at least two rollers which are disposed one behind the other in the direction of travel of the machine, a rigid frame in which the rollers are mounted for rotation, at least two vibration producing assemblies, one associated with each of the rollers and effective to impart vibration to its associated roller, one of the vibration producing devices operating at a different frequency than the other vibration producing device.

It has been found that earths of different consistencies and types must be compacted at different vibrational frequencies for optimum compacting efficiency. For example, road ballast such as gravel is most efficiently compacted at one vibrational frequency, a black top road surface is most efficiently compacted at a second vibrational frequency, and a soft clay soil is most efficiently compacted at still a different vibrational frequency. In order to achieve the best possible results it has been necessary in the past to have available a multiplicity of road rollers to provide the different vibrational frequencies for optimum compaction of the various clays, earths and other surfaces. With the vibrating roller compactor of this invention only one machine is required because the machine produces sweep frequency type oscillations in a relatively wide band. The varying frequencies of vibration of the rollers impacts the rollers on the ground so that all the particle sizes and consistencies of soil encountered by the rollers are effectively compacted to the same degree. Thus, virtually any consistency or type of surface to be compacted is impacted by the rollers in a range of frequencies which includes the optimum frequency. Correspondingly, one and the same roller type vibrating compactor provides for optimum compaction of road surfaces and other applications where different consistencies of earth are encountered.

A distinct advantage of the vibrating roller of this invention is that the individual rollers are subjected to varying vibrational frequencies. Such varying vibrational frequencies occur irrespective of the phase relationship or chronological sequence of the vibrational impacts imparted to the rollers which in turn are transmitted to the ground via the rollers. In the preferred embodiment, for example, the vibration assembly for one of the rollers imparts vibration to the roller at a first frequency, for example, at a frequency of cycles per second and the vibration assembly for the other roller imparts a vibration at a lower frequency, for example, 30 cycles per second. The apparent result is that one roller always impacts the ground at a constant higher vibrational frequency than the constant lower vibrational frequency of the other roller. However, by mounting the rollers on a common rigid frame each roller is in fact vibrated at a primary frequency which is the frequency of vibration of the vibration assembly associated with the roller, and in addition, is vibrated at sweep frequencies in a band on each side of the primary frequency to provide the range of frequencies required to compact virtually any earth consistency encountered by the rollers.

Advantageously, each vibration assembly includes a rotatable shaft with eccentrically mounted or unbalanced weights thereon. By driving the shafts at different speeds, the impacts which the rollers exert on the earth occur in a predetermined sequence even when the unbalanced weights are offset relative to each other since the phase relationship of the vibrations changes as a result of the different frequencies. Hence, the impacts shift chronologically during rotation of the weights. It has also been found that the effect of operating the eccentric weights at different frequencies is enhanced if the weights are arranged initially at an angle smaller than 180 relative to each other. In this latter arrangement, the direction of the vibrational frequencies are in phase only intermittantly with the result that each roller is in fact vibrated at a primary frequency including a band of frequencies resulting from vibrating another roller on the same rigid frame at a different frequency and out of phase with the first frequency.

Another embodiment of the vibrating roller of this invention attains further improved efficiency by use of a heavier unbalanced or eccentric weight with one roller and a lighter unbalanced weight with the other roller. In this embodiment, the vibrating assembly operating at the lower frequency has an eccentric weight of greater mass than the vibrating assembly operating at the higher frequency. In addition, the vibrating assembly with the heavier weight can be associated with a roller which is heavier than the other lighter roller vibrated by a lighter weight at a higher frequency. By properly arranging weights of selected ,mass with rollers of selected weight, the extent of comcan be precisely controlled. Correspondingly, by ap- V propriate selection of the frequencies, masses of the unbalanced weights, and size and weight of the rollers,

wide variation in the frequency of an intensity of the impacts delivered to the earth to be compacted can be obtained.

Numerous other objects, features, and advantages of this invention will become apparent with reference to the drawings which show preferred embodiments of the invention and in which:

FIG. 1 is a diagrammatic partial sectional view in side elevation showing one embodiment of earth compacting machine according to this invention;

FIG. 2 is a partial view corresponding to FIG. 1 and showing a different embodiment;

FIG. 3 is a view corresponding to FIG. 2 and showing another embodiment of the invention;

FIG. 4 is a view in section taken along line 44 of FIG. 3; and FIGS. 5-8 are diagrammatical views in side elevation showing the respective positions of the unbalanced weights relative to each other during a complete cycle of rotation of one of the weights, for a particular embodiment of the invention.

Referring now to the drawings in detail and particularly to FIG. 1, roller type earth compacting machine 1 has two rollers 2 and 3 mounted for rotation in a rigid frame 40, with the rollers arranged one behind the other in the direction of travel of the compacting machine. Frame 40 includes rigid side plates 4 and 5 at opposite sides of the rollers (FIG. 4) and a rigid cover plate 6 extending between and secured to the side plates.

Both rollers 2 and 3 are mounted for rotation between the side plates 4 and 5 (FIG. 4). The rotational mounting at side plate 5 includes a stub axle assembly 7, one secured to each of the rollers 2 and 3, and which stub axles are mounted for rotation respectively in bearings 8 supported by the side plate 5. The mounting arrangement at side plate 4 includes a stub axle sleeve 7a, one for each of the rollers 2 and 3, and bearings 80 mounted in the side plate 4 and through which the stub axle sleeves extend.

The roller type compacting machine is selfpropelled. As shown at FIG. 4, drive gear 9 (which is driven by a motor) meshes with idler gears 10 which drive the respective rollers in the same direction via the gears 11 keyed respectively to the stub axle sleeves 7a of the respective rollers.

A vibration assembly is associated with each roller for imparting vibration to the roller. The vibration assemblies for the respective rollers 2 and 3 include the shafts 12 and 13 respectively, which are journalled for rotation at their inner ends on bearings 16 in the stub axle shafts 7, and are similarly journalled for rotation at their other ends on bearing 16 in the stub axle sleeves 7a. The shafts 12 and 13 have projecting end portions 12a and 130, respectively, which project outwardly beyond the gears 9-11. Weights are eccentrically mounted on shaft 12 so rotation of shaft 12 vibrates roller 2, and weights 14 are eccentrically mounted on shaft 13 so rotation of shaft 13 vibrates roller 3. Shafts 12 and 13 rotate about the same axes as the respective rollers 2 and 3.

Mounted on the end 12a of shaft 12 is a pulley assembly including pulleys 17 and 17a, and mounted on the end 13a of shaft 13 is a pulley 18. The spur gears 9-11 are mounted in a first housing 19 closely adjacent to and connected to side plate 4. Similarly, a housing 20 extends over and encloses the space occupied by the pulleys 17, 17a and 18. Housing 20 can be secured to housing 19 as shown at FIG. 4. A tow bar 21 can be connected to coverplate 6 to facilitate transporting the roller compacting machine. I

Forward and reverse movement of the roller compactor is controlled by a lever 22 which controls the direction the rollers are driven by motor 23. As shown at FIG. 1, motor 23 is mounted on frame 4a at a location above the rollers 2 and 3 and is preferably located midway between the respective axes of rotation of the rollers. As previously explained, the machine is propelled by driving the rollers 2 and 3 and such driving is accomplished by the gears 9-1 1. Advantageously, gear 9 is driven by motor 23 through a suitable transmission (not shown) including appropriate reduction gears to drive the rollers at the usual slow speed. In addition, the shafts 12 and 13 are driven by a power takeoff from motor 23, this drive including a drive pulley 24 driven by the motor and a belt 25 which extends around pulley 17a on shaft 12 and drive pulley 24. As shown at FIGS. 1 and 4, shaft 13 is driven from shaft 12 by a belt 26 which extends around the respective pulleys 17 and 18 on shaft ends 12a and 13a respectively. The diameter of pulley 18 is greater than the diameter of pulley l7 and correspondingly, shaft 13 and its weights 14 rotate at a slower speed than shaft 12 and its weights 15. While, in the preferred embodiment of a vibrating road roller according to this invention, the diameter of pulley 18 is twice the diameter of pulley 17 so shaft 13 rotates at one-half the speed of shaft 12, the ratio of the diameters of pulley 17 to pulley 18 can be any desired ratio, for example, 1:3, 1:4 or 2:1, rather than the embodiment shown where the ratio is l :2.

With reference to the vibrating roller type compacting machine of FIG. 1, the ratio of the diameter of pulley 17 to to pulley 18 is 2:1 The unbalanced weights 14 and 15 are each of the same mass and size and the rollers 2 and 3 are similarly of the same mass but one of the rollers can be of a larger diameter. Hence, the amplitude of the vibrations produced by weights 14 and 15 when shafts 12 and 13 are driven is the same, but the frequencies of these vibrations are different. In addition, it will be observed with reference to FIG. 1, that in the rotational positions shown, weights 14 and 15 are displaced relative to each other, and such displacement provides an advantage which will subsequently be described in detail.

The vibrating roller type earth compacting machine 27 of FIG. 2' is essentially the same as the machine 1 of FIG. 1 save that the weights 14a of machine 27 are heavier than the weights 14 of machine 1. By the use of heavier weights 14a the amplitude of the vibration of shaft 13 is greater for the machine 27 than it is for the machine 1. In the embodiment of FIG. 2 the rollers 2 and 3 have the same weight as in the embodiment of FIG. 1 and the pulleys 17 and 18 have the same speed ratio of 2:l. With all features the same save that weights 14a are heavier than weights 14, greater vibrational forces are exerted on roller 3 by shaft 12 and weights 14a than are exerted on the roller 3 by the weights 14 of the FIG. 1 embodiment. Correspondingly, weights 14a are also heavier than weights 15 of the machine 27 and the amplitude of the vibration on roller 3 is greater than the vibration on roller 2.

However, the heavier weights 14a rotate at a lower speed than the lighter weights 15, and correspondingly, shaft 13 vibratesat a lower frequency than shaft 12. Correspondingly, the impacting forces in the machine 27 of FIG. 2 are distributed differently from the machine 1. 1

FIG. 3 shows another embodiment which represents a variation over the constructions of FIGS. 1 and 2. The roller type earth compacting machine 28 of FIG. 3 includes the same weights l5 and714a as the embodiment of FIG. 2. In all details machine 27 is identical to machine 28 except that a heavier roller 3a is provided for machine 28. As shown for the machine 28, roller 3a has a rim which is substantially thicker and correspondingly, heavier than the rim of the roller 3 of the embodiments of FIGS. 1 and 2. Otherwise, the construction of the machine 28is the same as the construction of the machine 27 of FIG. 2. In the FIG. 3 embodiment it is to be observed with particularity that the heavier slower rotating weights 14a are associated with the heavier roller 3:: whereas the lighter faster rotating weights are associated with the lighter roller 2 By virtue of this arrangement, the distribution of the vibrational frequencies between the rollers 2 and 3a differs from the distribution of the frequencies for the embodiments of FIGS. 1 and 2. Advantageously, the ratio. of pulley 17 to pulley 18 is 2:1. In the embodiment of FIG. 3, roller 3a has a mass twice the mass of roller 2, weights 14a has a mass which is twice the mass of weights 15, and weights 14a rotate at a speed which is one-half the speed of rotation of weights 15. Correspondin'gly, it can aptly be said that the ratio of the frequency of vibration of the vibration assemblies varies inversely with the respective unbalanced weights and roller weights.

In the embodiments of FIGS. l-3, pulleys l7 and 17a rotate in a clockwise direction and the shafts rotate in the same direction in the diagrammatic views of FIGS. 5-8, with reference to which the preferred rotational displacement of and operation of the weights will now be explained. I

With reference to FIG. 8, it will be observed that weights 15 which have the smaller mass, and weights 14a which have the. larger mass, simultaneously occupy positions wherein the centers of gravity of these weights are directly above or on top of the respective axes of the shafts l2 and 13. However, as previously explained, shaft 12 rotates at a speed which is twice the speed of rotation of shaft 13. Correspondingly, when shaft 12 and weights 15 have rotated 180 to the position of FIG. 5 where the center of gravity of weights 15 is immediately below the axis of shaft 12, weights 14a have only rotated 90 so their center of gravity is directly to the right of the axis of shaft 13. When weights 15 and shaft 12 have rotated an additional 180 to the FIG. 6 position, the center of gravity of weights 15 is again directly above the axis of shaft 12 whereas shaft 13 and weights 14a have only rotated an additional 90 so the center of gravity of weights 14a is now immediately beneath shaft 13. After another 180 of rotation of weights 15 to the position of FIG. 7, the center of gravity of weights 15 is again below shaft 12 whereas weights 14a have only rotated an additional 90 so their center ofgravity is horizontally to the left of shaft 13. Upon another 180 of rotation of shaft 12 2:1, it is to be noted with particularity that in no relative rotational position of the two weights do the weights act either horizontally outwardly simultaneously or horizontally inwardly simultaneously. This phasing of the weights substantially reduces stresses acting on the shafts and bearings of the machine as well as on the machine frame 4a and rollers 2 and 3. An additional advantage of this arrangement wherein weights l5 and 140 are simultaneously up at least once during two complete revolutions of weight 15 is that simultaneous upwardly directed unweighting forces act on the frame 4a and rollers 2 and 3 and facilitate steering and turning the machine at the instant of such unweighting. I

During operation of the compacting machine 1 of FIG. 1 rollers 2 and 3 of the machine are driven by motor 23 to propel the machine. In addition, motor 23 rotates shaft 12 and its associated weights 15, and

shafts l3 and its weights 14 are driven from shaft 12 at a speed which is half the speed of rotation of shaft 12. Hence, the frequency of vibration of shaft 12 and weights I5 is twice the frequency of vibrationof shaft 13 and weights l4. Advantageously, each shaft is driven at a substantially constant speed so the frequency of vibration of shaft 12 is constant and frequency of vibration of shaft 13 is constant. However, even if the speed of shaft 12 changes the speed ratio of 2:1 remains constant because shaft 12 drives shaft 13. Upon initial consideration it would appear that the effect of the constant frequency vibrations of shaft 12 would be to vibrate roller 2 at a constant frequency and the constant frequency vibrations of shaft 13 would be 'to vibrate roller 3 at a constant frequency. Surprisingly, however, roller 2vibrates at varying frequencies in a recurring pattern from a frequency above the frequency of vibration of shaft 12 to a frequency below the frequency of vibration of shaft 12, and similarly, roller 3 vibrates at varying frequencies in a recurring pattern from a frequency above the frequency of vibration of shaft 13 to a frequency below the frequency of vibration of shaft 13. It is believed that some of the vibration from the shaft 13 is transmitted to roller 2 via the rigid frame 4a and some of the vibration from shaft 12 is transmitted to the roller 3 also via the rigid frame 4a. Hence, instead of simple sinusoidal vibration of the rollers 2 and 3 as a result of the vibrations from shafts 12 and 13 respectively, the vibrations of each of the rollers occur in a complex wave form which includes a band or range of frequencies above and below the primary 15, there is a different relationship between the amplitudes of, as well as the frequencies of, vibration of the shafts l2 and 13. By virtue of this difference in amplitude from the embodiment of FIG. 1, substantially different vibrational characteristics are imparted to the rollers 2 and 3 of the machine 27 of FIG. 2. It has been found, surprisingly, that varying only the mass of the weights relative to each other without changing the speed of rotation of the respective weights, provides not only a different intensity of impaction but also varies the band width of the frequencies of vibration of the rollers 2 and 3.

In the embodiment of FIG. 3 where roller 3 has a substantially greater mass than roller 2, the vibrational characteristics are again different. By changing the mass of one of the rollers, the amplitude of the vibration transmitted by the shaft 12 to the roller 3 and by the shaft 13 to the roller 2 via rigid frame 4a changes significantly, and correspondingly, the band width of the frequencies of vibration of each roller are correspondingly changed from the embodiments of FIGS. 1 and 2.

By virtue of the arrangements of the preferred embodiments shown and described herein each roller is vibrated at varying frequencies from above to below and again above a principle frequency in a recurring pattern, even though the vibration producing shaft and weights for each roller rotate at, and vibrate at a relatively constant frequency.

While several preferred embodiments of the roller type compactor according to this invention have been shown and described in detail, numerous changes can be made in the embodiments disclosed herein without departing from the scope of this invention as defined in the specification and the appended claims.

l claim:

1. A roller type earth compactor comprising a. a rigid frame,

b. a first roller journalled on said frame for rotation,

c. a second roller journalled on said frame for rotation and disposed behind the first roller in the direction of travel of the earth compactor,

. a first shaft and a first unbalanced weight mounted on said first shaft and rotatable about the axis of said first roller for producing vibration,

a second shaft and a second unbalanced weight mounted on said second shaft and rotatable about the axis of said second roller for producing vibration,

f. first and second pulleys operatively connected to said first and second shafts respectively, said second pulley have a greater diameter than said first pulley,

motor means mounted on said frame, and

. belt means connecting said motor means and pulleys,

i. whereby said first weight is driven at a first rate to generate a first frequency of vibration and said second weight is driven at a second rate slower than said first rate to generate a second frequency of vibration less than said first frequency of vibration, and said first and second rollers vibrate at varying frequencies in a reoccurring pattern from a frequency above to a frequency below said frequencies of vibration of said first and second rates respectively.

2. A roller type compactor according to claim 1 wherein the relative diameters of said first and second pulleys are such that said first and second weights rotate at rates relative to each other whereby said first weight vibrates at a frequency which is an integer multiple of the frequency of vibration of said second weight.

3. A roller type compactor according to claim 2 wherein the relative diameters of said first and second pulleys are such that said first and second weights are driven synchronously at different speeds with the rotational positions of said weights displaced relative to each other.

4. A roller type compactor according to claim 2 wherein said first and second weights are rotated and positioned relative to each other such that both weights occupy a top vertical position simultaneously at least once during several complete revolutions of said first weight, whereby an upwardly directed force simultaneously acts on both said first and second rollers to provide an unweighting action facilitating steering movement of the compacting machine.

5. A roller type compactor according to claim 4 wherein said weights initially occupy a top vertical position, and said driving means is adapted to rotate said first weight at a speed which is twice the speed at which said driving means rotates said second weight.

6. A roller type compactor according to claim 1 wherein said belt means comprises a belt extending between said pulleys and a further belt extending between said motor means and one of said pulleys.

7. A roller type compactor according to claim 1 further comprising transmission means operatively connecting said motor means to said first and second rollers to propel said earth compactor.

8. A roller type compactor according to claim 1 wherein said first and second weights and first and second rollers have the same masses respectively whereby said first and second rollers vibrate at the same amplitude.

9. A roller type earth compactor comprising a rigid frame,

a first roller journalled on said frame for rotation,

a second roller journalled on said frame for rotation and disposed behind the first roller in the direction of travel of the earth compactor,

. a first unbalanced weight rotatable about the axis of said first roller for producing vibration,

e. a second unbalanced weight rotatable about the axis of said second roller for producing vibration, said second weight having a greater mass than said first weight, and

f. means for driving said first weight at a first rate to generate a first frequency of vibration and said second weight at a second rate slower than said first rate to generate a, second frequency of vibration less than said first frequency of vibration,

. whereby said first and second rollers vibrate at different amplitudes and at varying frequencies in a reoccurring pattern from a frequency above to a frequency below said frequencies of vibration of said first and second rates respectively.

10. A roller type compactor according to claim 9 wherein said driving means is adapted to rotate said first and second weights at rates relative to each other such that said first weight vibrates at a frequency which is an integer multiple of the frequency of vibration of said second weight.

11. A roller type compactor according to claim 10 wherein said driving means is adapted to drive said first and second weights synchronously at different speeds with the rotational positions of said weights displaced 90 relative to each other.

12. A roller type compactor according to claim 10 wherein said first and second weights are rotated and positioned relative to each other such that both weights occupy a top vertical position simultaneously at least once during several complete revolutions of said first weight, whereby an upwardly directed force simultaneously acts on both said first and second rollers to provide an unweighting action facilitating steering movement of the compacting machine.

13. A roller type compactor according to claim 12 wherein said weights initially occupy a top vertical position, and said driving means is adapted to rotate said first weight at a speed which is twice the speed at which said driving means rotates said second weight.

14. A roller type compactor according to claim 9 wherein said drive means comprises first and second shafts operatively connected to said first and second weights respectively, first and second pulleys operatively connected to said first and second shafts respectively, said second pulley having a greater diameter than said first pulley, motor means, and belt means connecting said motor means and pulleys.

15. A roller type compactor according to claim 9 wherein said belt means comprises a belt extending between said pulleys and a further belt extending between said motor means and one of said pulleys.

16. A roller type compactor according to claim 9 wherein said driving means is adapted to rotate said first and second rollers to propel said earth compactor.

17. A roller type compactor according to claim 9 wherein said second roller has a greater mass than said first roller whereby the ratio of the frequency of vibration of said unbalanced weights varies inversely with the respective masses of said unbalanced weights and rollers.

18. A roller type compactor according to claim 17 wherein said driving means is adapted to rotate said first and second weights at rates relative to each other such that said first weight vibrates at a frequency which is an integer multiple of the frequency of vibration of said second weight.

19. A roller type compactor according to claim 18 wherein said driving means is adapted to drive said first and second weights synchronously at different speeds with the rotational positions of said weights displaced 90 relative to each other.

20. A roller type compactor according to claim 18 wherein said first and second weights are rotated and positioned relative to each other such that both weights occupy a top vertical position simultaneously at least once during several complete revolutions of said first weight, whereby an upwardly directed force simultaneously acts on both said first and second rollers to provide an unweighting action facilitating steering movement of the compacting machine.

21. A roller type compactor according to claim 20 wherein said weights initially occupy a top vertical position, and said driving means is adapted to rotate said first weight at a speed which is twice the speed at which said driving means rotates said second weight.

22. A roller type compactor according to claim 17 wherein said drive means comprises first and second shafts operatively connected to said first and second weights respectively, first and second pulleys operatively connected to said first and second shafts respectively, said second pulley having a greater diameter than said first pulley, motor means, and belt means connecting said motor means and pulleys.

23. A roller type compactor according to claim 17 wherein said belt means comprises a belt extending between said pulleys and a further belt extending between said motor means and one of said pulleys.

24. A roller type compactor according to claim 17 wherein said driving means is adapted tordtate said first and second rollers to propel said earth compactor.

25. A roller type earth compactor comprising a. a rigid frame,

b. a first roller journalled on said frame for rotation,

c. a second roller journalled on said frame forrotation and disposed behind the first roller in the direction of travel of the earth compactor, said second roller having a greater mass than said first roller,

. a first shaft and a first unbalanced weight mounted on said first shaft and rotatable about the axis of said first roller for producing vibration,

e. a second shaft and a second unbalanced weight mounted on said second shaft and rotatable about the axis of said second roller for producing vibration, said second weight having a greater mass than said first weight,

f. first and second pulleys operatively connected to said first and second shafts respectively, said second pulley having a greater diameter than said first pulley, motor means mounted on said frame, and

. belt means connecting said motor means and pulleys,

. whereby said first weight is driven at a first rate to generate a first frequency of vibration and said second weight is driven at a-second rate slower than said first rate to generate a second frequency of vibration less than said first frequency of vibration, and

j. said first and second rollers vibrate at different amplitudes and at varying frequencies in a reoccurring pattern from a frequency above to a frequency below said frequencies of vibration of said first and second rates respectively.

a: a: is a: e 

1. A roller type earth compactor comprising a. a rigid frame, b. a first roller journalled on said frame for rotation, c. a second roller journalled on said frame for rotation and disposed behind the first roller in the direction of travel of the earth compactor, d. a first shaft and a first unbalanced weight mounted on said first shaft and rotatable about the axis of said first roller for producing vibration, e. a second shaft and a second unbalanced weight mounted on said second shaft and rotatable about the axis of said second roller for producing vibration, f. first and second pulleys operatively connected to said first and second shafts respectively, said second pulley have a greater diameter than said first pulley, g. motor means mounted on said frame, and h. belt means connecting said motor means and pulleys, i. whereby said first weight is driven at a first rate to generate a first frequency of vibration and said second weight is driven at a second rate slower than said first rate to generate a second frequency of vibration less than said first frequency of vibration, and said first and second rollers vibrate at varying frequencies in a reoccurring pattern from a frequency above to a frequency below said frequencies of vibration of said first and second rates respectively.
 2. A roller type compactor according to claim 1 wherein the relative diameters of said first and second pulleys are such that said first and second weights rotate at rates relative to each other whereby said first weight vibrates at a frequency which is an integer multiple of the frequency of vibration of said second weight.
 3. A roller type compactor according to claim 2 wherein the relative diameters of said first and second pulleys are such that said first and second weights are driven synchronously at different speeds with the rotational positions of said weights displaced 90* relative to each other.
 4. A roller type compactor according to claim 2 wherein said first and second weights are rotated and positioned relative to each other such that both weights occupy a top vertical position simultaneously at least once during several complete revolutions of said first weight, whereby an upwardly directed force simultaneously acts on both said first and second rollers to provide an unweighting action facilitating steering movement of the compacting machine.
 5. A roller type compactor according to claim 4 wherein said weights initially occupy a top vertical position, and said driving means is adapted to rotate said first weight at a speed which is twice the speed at which said driving means rotates said second weight.
 6. A roller type compactor according to claim 1 wherein said belt means comprises a belt extending between said pulleys and a further belt extending between said motor means and one of said pulleys.
 7. A roller type compactor according to claim 1 further comprising transmission means operatively connecting said motor means to said first and second rollers to propel said earth compactor.
 8. A roller type compactor according to claim 1 wherein said first and second weights and first and second rollers have the same masses respectively whereby said first and second rollers vibrate at the same amplitude.
 9. A roller type earth compactor comprising a. a rigid frame, b. a first roller journalled on said frame for rotation, c. a second roller journalled on said frame for rotation and disposed behind the first roller in the direction of travel of the earth compactor, d. a first unbalanced weight rotatable about the axis of said first roller for producing vibration, e. a second unbalanced weight rotatable about the axis of said second roller for producing vibration, said second weight having a greater mass than said first weight, and f. means for driving said first weight at a first rate to generate a first frequency of vibration and said second weight at a second rate slower than said first rate to generate a second frequency of vibration less than said first frequency of vibration, g. whereby said first and second rollers vibrate at different amplitudes and at varying frequencies in a reoccurring pattern from a frequency above to a frequency below said frequencies of vibration of said first and second rates respectively.
 10. A roller type compactor according to claim 9 wherein said driving means is adapted to rotate said first and second weights at rates relative to each other such that said first weight vibrates at a frequency which is an integer multiple of the frequency of vibration of said second weight.
 11. A roller type compactor according to claim 10 wherein said driving means is adapted to drive said first and second weights synchronously at different speeds with the rotational positions of said weights displaced 90* relative to each other.
 12. A roller type compactor according to claim 10 wherein said first and second weights are rotated and positioned relative to each other such that both weights occupy a top vertical position simultaneously at least once during several complete revolutions of said first weight, whereby an upwardly directed force simultaneously acts on both said first and second rollers to provide an unweighting action facilitating steering movement of the compacting machine.
 13. A roller type compactor according to claim 12 wherein said weights initially occupy a top vertical position, and said driving means is adapted to rotate said first weight at a speed which is twice the speed at which said driving means rotates said second weight.
 14. A roller type compactor according to claim 9 wherein said drive means comprises first and second shafts operatively connected to said first and second weights respectively, first and second pulleys operatively connected to said first and second shafts respectively, said second pulley having a greater diameter than said first pulley, motor means, and belt means connecting said motor means and pulleys.
 15. A roller type compactor according to claim 9 wherein said belt means comprises a belt extending between said pulleys and a further belt extending between said motor means and one of said pulleys.
 16. A roller type compactor according to claim 9 wherein said driving means is adapted to rotate said first and second rollers to propel said earth compactor.
 17. A roller type compactor according to claim 9 wherein said second roller has a greater mass than said first roller whereby the ratio of the frequency of vibration of said unbalanced weights varies inversely with the respective masses of said unbalanced weights and rollers.
 18. A roller type compactor according to claim 17 wherein said driving means is adapted to rotate said first and second weights at rates relative to each other such that said first weight vibrates at a frequency which is an integer multiple of the frequency of vibration of said second weight.
 19. A roller type compactor according to claim 18 wherein said driving means is adapted to drive said first and second weights synchronously at different speeds with the rotational positions of said weights displaced 90* relative to each other.
 20. A roller type compactor according to claim 18 wherein said first and second weights are rotated and positioned relative to each other such that both weights occupy a top vertical position simultaneously at least once during several complete revolutions of said first weight, whereby an upwardly directed force simultaneously acts on both said first and second rollers to provide an unweighting action facilitating steering movement of the compacting Machine.
 21. A roller type compactor according to claim 20 wherein said weights initially occupy a top vertical position, and said driving means is adapted to rotate said first weight at a speed which is twice the speed at which said driving means rotates said second weight.
 22. A roller type compactor according to claim 17 wherein said drive means comprises first and second shafts operatively connected to said first and second weights respectively, first and second pulleys operatively connected to said first and second shafts respectively, said second pulley having a greater diameter than said first pulley, motor means, and belt means connecting said motor means and pulleys.
 23. A roller type compactor according to claim 17 wherein said belt means comprises a belt extending between said pulleys and a further belt extending between said motor means and one of said pulleys.
 24. A roller type compactor according to claim 17 wherein said driving means is adapted to rotate said first and second rollers to propel said earth compactor.
 25. A roller type earth compactor comprising a. a rigid frame, b. a first roller journalled on said frame for rotation, c. a second roller journalled on said frame for rotation and disposed behind the first roller in the direction of travel of the earth compactor, said second roller having a greater mass than said first roller, d. a first shaft and a first unbalanced weight mounted on said first shaft and rotatable about the axis of said first roller for producing vibration, e. a second shaft and a second unbalanced weight mounted on said second shaft and rotatable about the axis of said second roller for producing vibration, said second weight having a greater mass than said first weight, f. first and second pulleys operatively connected to said first and second shafts respectively, said second pulley having a greater diameter than said first pulley, g. motor means mounted on said frame, and h. belt means connecting said motor means and pulleys, i. whereby said first weight is driven at a first rate to generate a first frequency of vibration and said second weight is driven at a second rate slower than said first rate to generate a second frequency of vibration less than said first frequency of vibration, and j. said first and second rollers vibrate at different amplitudes and at varying frequencies in a reoccurring pattern from a frequency above to a frequency below said frequencies of vibration of said first and second rates respectively. 